光频域反射技术中激光相位噪声影响分析

Phase Noise Analysis of Optical Frequency Domain Reflectometry

研究了光频域反射技术(OFDR)中因激光线宽有限而造成的激光相位噪声对系统性能的影响。理论推导了相位噪声的分布函数,仿真分析和实验测试了激光相位噪声与激光相干长度、反射信号强度之间的内在关联性。研究结果表明,激光相位噪声是OFDR中的重要噪声来源,影响着系统的测试精度和可测距离,当测试距离接近相干长度、链路中存在强的反射信号时,激光相位噪声的影响将更加严重、影响范围也将增加。因此,在OFDR的设计和应用中必须对激光相位噪声问题予以高度关注和设计考虑。

The analysis of the phase noise effect in the optical frequency domain reflectometry（OFDR） is presented.A model of distribution function of phase noise is built.Simulations and further experiments demonstrate the effect of phase noise on the measurement of reflection signal and Rayleigh backscattering signal due to the finite laser linewidth and the influence of phase noise under different reflectivities.The results show the phase noise is the main issue which limits the resolution and measurement range.Under condition of the measurement range reaching the coherent length or strong reflection in fiber links,the much more significant phase noise will affect reflection signal of a longer range.According to the analysis,we should pay much more attention to the phase noise of laser while designing OFDR systems.